This section gives you a few examples of chainmail rules.

If the message sender is in "customer.com" domain and the recipient is not the support mailbox, copy the message to the local manager:

Rule "CopyManager"
If Sender "@customer.com" and not Rcpt "support@mycompany.com"
Action AddRcpt "manager"

If the message is received from the local subnet 192.168.1. and contains words "support request" in the subject, accept it without applying any further rules:

Rule "AcceptLocalSupport"
If ClientAddr "192.168.1." and Header "Subject" "[Ss]upport.*request"
Action Accept

If the message is not addressed to postmaster and is suspicious of being spam, reject it:

Rule "RejectSpam"
If not Rcpt "postmaster@" and (BodyMatch "low rate mortgage" 
  or ClientName "*.spam.com")
Action Reject "" "" "Spam suspected"